Conventional thyristors of a p-n-p-n structure are high in base resistance, and hence have the defects that they are not sensitive enough to light and are low in operating speed.
FIG. 1 shows a conventional light-triggered thyristor. This has a p-n-p-n four-layered struct re, 1 being an anode electrode, 2 a cathode electrode and 3 a gate electrode. 10 is a light input directed to the thyristor.
When irradiated by light, the thyristor conducts. Sometimes the gate electrode 3 is not activated. Since the conventional light trigger thyristor is high in the resistance of its p-type base, as shown in FIG. 1, it takes time for the entire device to turn ON. Because of this, the frequency at which the thyristor can be switched is very low.
An object of the present invention is to provide a photothyristor which is higher in photo sensitivity and faster in switching operation than the above mentioned conventional light trigger thyristor.